Huge potential
The Need for Carbon Removal Projects
As climate change intensifies through severe storms, wildfires, and flooding, reducing greenhouse gas (GHG) emissions is crucial. Transitioning to electric vehicles, deploying solar panels, and reducing deforestation are essential steps. However, the latest climate science indicates that these efforts alone will not limit temperature rise to 1.5°C (2.7°F), necessary to prevent catastrophic climate change impacts.
Why Carbon Removal is Necessary
Meeting climate goals requires carbon dioxide removal (CDR) technologies that directly remove carbon from the air, potentially at a billion-tonne scale by mid-century. Carbon removal balances residual emissions and reduces atmospheric carbon dioxide concentrations, mitigating devastating climate impacts. The United States, as the largest historical CO2 emitter, must lead in carbon removal.
Forms of Carbon Removal
Carbon removal can take various forms:
- Natural solutions: tree growth and soil carbon sequestration
- Technological solutions: accelerating natural processes or directly capturing CO2
Direct Air Capture (DAC)
DAC is a promising technological carbon removal method:
- Uses chemical reactions to capture CO2 from air
- Relatively space-efficient and flexible deployment
- Can be built on marginal land or near geological storage sites
How DAC Works
- Chemicals selectively react with and trap CO2 from air
- Heat releases captured CO2 from solvents or sorbents for reuse
- Captured CO2 can be:
- Injected underground for sequestration
- Used in products (concrete, plastic) for long-term sequestration
- Used in synthetic fuels (jet fuel) as a more favorable substitute
Maximizing Climate Benefit
To achieve significant climate benefits, most captured CO2 should be stored underground rather than used in products.
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The Critical Need for Carbon Removal in the Fight Against Climate Change
As the effects of climate change continue to intensify through more severe storms, devastating wildfires, and catastrophic flooding, the urgent need to reduce greenhouse gas (GHG) emissions has become increasingly evident. Transitioning to electric vehicles, deploying solar panels, reducing deforestation, and implementing other emission-reduction strategies are essential steps toward mitigating the worst impacts of climate change.
However, the latest climate science indicates that these efforts alone will not be sufficient to limit global temperature rise to 1.5°C (2.7°F) above pre-industrial levels, the threshold necessary to prevent the most catastrophic climate change impacts. In fact, current projections suggest that even if all countries meet their Paris Agreement targets, global temperatures are likely to rise by 2.5-3.2°C (4.5-5.8°F) by the end of the century.
Why Carbon Removal is Necessary
Meeting climate goals requires not only reducing GHG emissions but also actively removing carbon dioxide from the atmosphere. Carbon dioxide removal (CDR) technologies, which can directly remove carbon from the air, will likely need to be deployed at a billion-tonne scale by mid-century. Carbon removal serves two critical purposes:
- Balancing residual emissions: Even with aggressive emission reductions, some sectors (e.g., aviation, cement production) will continue to emit GHGs. Carbon removal can offset these residual emissions.
- Reducing atmospheric carbon dioxide concentrations: Removing excess carbon dioxide from the atmosphere helps mitigate devastating climate impacts.
The United States, as the largest cumulative historical emitter of CO2, has a responsibility to lead in carbon removal efforts.
Forms of Carbon Removal
Carbon removal can take various forms:
- Natural solutions:
- Tree growth and reforestation
- Soil carbon sequestration through sustainable agriculture practices
- Wetland restoration
- Ocean fertilization
- Technological solutions:
- Accelerating natural carbon removal processes
- Directly capturing CO2 from the air using chemical or biological methods
Direct Air Capture (DAC): A Promising Technological Solution
DAC is a technological carbon removal method that shows significant promise:
- Uses chemical reactions to capture CO2 from air
- Relatively space-efficient and flexible deployment
- Can be built on marginal land or near geological storage sites, minimizing competition with other land uses
How DAC Works
- Chemicals selectively react with and trap CO2 from air
- Heat releases captured CO2 from solvents or sorbents for reuse
- Captured CO2 can be:
- Injected deep underground for sequestration in certain geologic formations
- Used in products (concrete, plastic) for long-term sequestration (decades or even centuries)
- Used in synthetic fuels (jet fuel) as a more favorable substitute for fossil fuels
Maximizing Climate Benefit
To achieve significant climate benefits, most captured CO2 should be stored underground rather than used in products. While utilizing CO2 in products can provide some climate benefits, the net carbon sequestration potential is often limited.
Scaling Up Carbon Removal
To meet climate goals, carbon removal must be scaled up rapidly:
- Developing and deploying new CDR technologies
- Improving efficiency and reducing costs
- Establishing policy frameworks and incentives to support CDR deployment
- Encouraging international cooperation and knowledge sharing
The fight against climate change requires a multifaceted approach that includes aggressive emission reductions, carbon removal, and innovative technologies. By prioritizing carbon removal and DAC, we can help mitigate the worst impacts of climate change and create a more sustainable future.
Technology like this has been mooted for years but faced huge engineering challenges and, until recently, was dismissed as a costly fantasy.
Now the first plants are coming online, with the Intergovernmental Panel on Climate Change (IPCC) recognizing that even if the world reduces its ongoing emissions as quickly as possible, there will still be too much CO2 in the atmosphere to avoid catastrophic levels of global warming. IPCC says, the world needs to both reduce future emissions and remove historical ones to reach a safe climate.
Experts say DAC could become a trillion-dollar global industry — if it can be deployed at scale.
Why not just plant more trees?
When Deanna D’Alessandro, a professor of chemistry at the University of Sydney, encountered the idea of mechanical carbon removal, she wondered if there wasn’t a simpler solution.
A tree, of course, is a pre-existing and relatively cheap technology that sequesters CO2 in wood and other biomass. When scaled up, it’s called a forest.
“My first thought was why not plant more trees,” Professor D’Alessandro said.
“And then I did the numbers and stood in awe of them.”
By her own calculations, using reforesting to capture Australia’s CO2 emissions for two years, (about 1 billion tonnes), would require an area of land equivalent to the size of New South Wales. “DAC could do the same with 99.7 per cent less space,” she said. “Not only do we not have the land, we don’t have the water to achieve natural sequestration.”
Mark Howden, director of the Climate Change Institute at the Australian National University, agrees. “The science is very clear that to keep temperatures down to [an increase of] 1.5C, we not only need to reduce greenhouse gas emissions, we also have to absorb CO2 from the atmosphere,” he said. “It’s increasingly clear that doing that just from planting trees and relying on farmers and soil carbon is not enough.”
How does direct air capture work?
DAC is just one of several proposed technologies designed to remove emissions from the atmosphere, which also include repurposing offshore oil and gas platforms to grow seaweed, and turn it into fire-resilient bricks.
DAC works a little bit like a household dehumidifier, but instead of stripping water out of the air, it removes carbon dioxide.
DAC would have to be scaled up enormously to be useful.(Supplied: Carbon Engineering)
The greatest challenge, says Professor D’Alessandro, is processing enough air to capture a significant amount of CO2, given the gas makes up just 0.04 per cent of the air we breathe.
“To be frank, it’s been one of the most interesting scientific problems in chemistry in the past 10 years,” Professor D’Alessandro said.
There are generally two approaches.
In the first, a fan pulls air into a structure lined with thin plastic surfaces that have potassium hydroxide solution flowing over them.
The solution chemically binds with the CO2 molecules, removing them from the air and trapping them in the liquid solution as a carbonate salt.
The second method uses a sponge-like filter that absorbs CO2 and is then reheated to release the gas into storage.
In the case of the plant in Iceland, the captured CO2 is injected about a kilometre underground into volcanic rock.
Over two years it reacts with the basalt to form a solid carbonate material.
The captured carbon dioxide is injected into the ground at these nearby pods.(Getty Images: Arnaldur Halldorsson)
But underground storage isn’t the only option, Professor Howden said.
“Probably the dumbest thing we can do with captured CO2 is put it in the ground,” he said.
“To my mind, if we’ve gone to the bother of capturing CO2 why not treat it as a resource?”
Another DAC company, Canada’s Carbon Engineering, plans to use captured CO2 as an input to make carbon-neutral synthetic fuels that can substitute for diesel, petrol, or jet fuel.
Other proposals include using CO2 in cement production and plastics manufacturing, which could make buildings and water bottles carbon negative.
Is this any different to carbon capture and storage?
CCS involves capturing CO2 at the site of production, such as a gas liquefaction plant or coal-fired power station, and then pumping it deep underground.
Instead of filtering the air, it filters emissions from a smokestack.
Though the Australian government has singled CCS out as a priority technology for emissions reduction, critics have said it’s a failure.
One of the major problems is CO2 leaking from underground reservoirs.
With DAC, there’s a much lower risk of leakage, Professor Howden said.
“With standard CCS you’re restricted in the geology to somewhere close to the point of combustion, whereas you can put a DAC system anywhere, so you find geology that’s suitable and locate it there.”
How much CO2 needs to be captured?
DAC would need to be enormously scaled up to be useful.
Even if the world reaches net zero by 2050, it will still be necessary to remove 5 to 14 billion tonnes of CO2 per year from the atmosphere from 2030 onwards to keep global warming below the 1.5C limit set by the Paris Agreement, according to a University of Melbourne report.
The DAC plant in Iceland, which is the world’s biggest, can capture and remove 4,000 metric tonnes of CO2 a year.
That’s about 10 million times less than annual global emissions.
At our current level of emissions, humanity is cancelling out the plant’s yearly efforts every three seconds.
The “mechanical tree” concept uses wind, rather than fans, meaning a much lower energy cost.(Supplied: Silicon Kingdom Holdings)
Daniel Egger, the chief commercial officer of Climeworks, the operator of the Iceland facility, said the company was on track for “megaton capacity” by the second half of this decade.
“To be an effective solution for climate change, an entire carbon removal industry will need to develop over a period of the next 10 to 20 years, creating capacities of at least 5 billion tonnes of carbon removal by 2050,” he said.
Professor Howden estimated DAC would ultimately account for a more modest amount of carbon removal.
“DAC of 1 to 1.5 billion tonnes of CO2 a year is potentially feasible,” he said.
What does it cost?
DAC is currently prohibitively expensive, mainly due to the cost of energy.
Climeworks has priced its DAC offsets at about $US775 ($1,094)a tonne and says this will fall as low as $US250 ($353) by the end of the decade.
The US Department of Energy recently announced a goal of slashing the cost to $US100 per tonne ($141) by the end of the decade.
That’s still a lot more expensive than offsetting CO2 by planting trees, which costs as little as $US20 ($28) per tonne.
Bushfires can release carbon sequestered in timber and undo millions of tonnes of offsets.(Supplied: Jochen Spencer)
So who’s paying Climeworks a premium for DAC offsets?
“We have an array of corporate clients such as Stripe, Audi, Shopify, Microsoft, Swiss Re, Boston Consulting Group,” Mr Egger said.
Microsoft, for instance, has committed to going carbon negative by 2030 and is investing $US1 billion ($1.4 billion) from 2020 to 2024 to “stimulate and accelerate the development of carbon removal technology.”
Is Australia doing DAC?
There are several proposed DAC projects in Australia, but nothing yet at a commercial scale.
Energy giant Santos struck a deal with CSIRO last November to trial the government agency’s new DAC technology in South Australia.
That same month, Elon Musk’s philanthropic research foundation awarded a University of Sydney team $250,000 to develop solar-powered DAC modules the size and shape of a two-person tent.
An illustration of the solar-powered DAC module technology developed at University of Sydney.(Supplied: Southern Green Gas)
These could be deployed in non-arable parts of Australia with high levels of solar radiation, said Professor D’Alessandro, a member of the team.
A start-up named Southern Green Gas (SGG) plans to produce and deploy at least some of these modules by the end of the year.
Australia’s abundant solar energy makes it an ideal location for DAC, Professor Howden said.
“DAC takes a lot of energy, so increasingly that will be sourced from renewables.
“And increasingly renewables are getting cheaper and cheaper and at some times of the day the costs are negative.”
But for the industry to prosper, it will need a price on carbon and more research funding for universities, he said.
It will also need public support, as the solar panels and wind capture systems used for DAC will take up land.
“Would the public like those sorts of things dotted across the landscape?” Professor Howden said.
“We need to put in place [systems of support for DAC] early and that requires proactivity, which requires vision and foresight.
“If we’re smart about this, this could be a billion-dollar earner for Australia.”